Studies of human prostatic nuclear phosphoproteins and associated enzymes are now in progress. Methods developed for studies of rat prostate nuclear phosphoproteins are used in these experiments except that modified procedures are necessary for the preparation of nuclei and chromatin from human prostatic tissue obtained at open resection, transurethral resection, and at autopsy (about 8 hr post-mortem). The protein/DNA of these preparations is 2.54 compared with 2.09 for rat chromatin. The preparations possess protein phosphokinase activity (PK) towards the model acidic protein substrate dephosphophosvitin (DPV); the conditions for optimal activity are slightly different from those observed with rat tissue preparation. The results obtained suggest that the human prostatic tissue obtained under either of the above conditions may be used for these biochemical studies, and experiments are underway to examine the above parameters in normal and neoplastic prostatic tissue. The non-histone proteins and phosphoproteins of prostatic nucleus have been implicated in the binding of androgen-receptor complex to the nucleus. We have previously shown that rat ventral prostate chromatin protein phosphorylation and associated PKs are androgen-sensitive. Studies of the effects of the antiandrogens cyproterone acetate (CA) and flutamide (F) yielded similar results as those obtained from orchiectomy of the adult animals. At 48 hours, after a daily dose of 10 mg of CA or F, the chromatin-associated PK towards DPV was declined by about 60%, a value comparable to that observed with chromatin preparations from castrated rats. Under all these conditions the PK towards lysine-rich histone was only slightly reduced, suggesting that the PKs involved in the phosphorylation of endogenous acidic phosphoproteins show greater sensitivity to the androgenic status of the animal.